When processing information in electronic devices, the information may originate in some analog form (e.g., as an analog signal), and analog-to-digital converter (ADC) systems are typically used to transform the analog signal into a digital signal for further processing. A conventional ADC system usually includes a core circuit that performs the analog-to-digital conversion and additional support circuitry coupled to the core circuit. Examples of the additional support circuitry include, but are not necessarily limited to, a reference circuit that sets the full-scale range of the core circuit and a scaling circuit that scales the analog input signals to fit into the full-scale operating range of the core circuit.
Most conventional ADC systems, such as one based on a redundant signed digit (RSD) cyclic system and the like, have separate circuit blocks for each of these functions (e.g., scaling and setting the full-scale range). In general, each of these circuit blocks includes an operational amplifier (OPAMP) in the respective circuit. When using an OPAMP, an offset error may be associated with the differential inputs of the OPAMP. The impact of this offset error is increased in conventional ADC systems using multiple OPAMPs to accomplish the analog-to-digital conversion. For example, the offset error associated with the OPAMP for the reference circuit, the offset error associated with the OPAMP for the scaling circuit, and the offset error associated with the OPAMP for the core converter circuit together contribute to the overall error of the ADC system. In some instances, the circuit blocks may be designed to minimize the offset error attributed to the OPAMPs but at the cost of increasing the complexity of the circuit block.
In addition to contributing offset error to the ADC system, the OPAMPs consume power during normal operation of the ADC system and occupy space. In portable devices, such as cellular phones, personal digital assistants, and the like, minimizing power consumption and device size are valuable design considerations. For example, mobile communication products place a premium on maximizing battery life.
Accordingly, a system for converting an analog signal to a digital signal having reduced power consumption and component size is desired. In addition, a system for converting an analog signal to a digital signal having reduced offset errors is desired. In addition, a method for converting an analog signal to a digital signal having reduced power consumption and component size is desired. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.